<template>
  <div class="pagination">

    <button :disabled="pageNo == 1" @click="$emit('getPage', pageNo - 1)">上一页</button>
    <button v-if="startEndNum.start > 1" @click="$emit('getPage', 1)" :class="{ active: pageNo == 1 }">1</button>
    <button v-if="startEndNum.start > 2" @click="$emit('getPage', 2)" :class="{ active: pageNo == 2 }">2</button>
    <button v-if="startEndNum.start > 3">···</button>
    <!-- 中间 -->
    <button v-for="(page, index) in startEndNum.end" :key="index" v-if="page >= startEndNum.start"
      @click="$emit('getPage', page)" :class="{ active: pageNo == page }">{{ page }}</button>

    <button v-if="startEndNum.end < totalPage - 1">···</button>
    <button v-if="startEndNum.end < totalPage" @click="$emit('getPage', totalPage)"
      :class="{ active: pageNo == totalPage }">{{ totalPage }}</button>
    <button :disabled="pageNo == totalPage" @click="$emit('getPage', pageNo + 1)">下一页</button>

    <button style="margin-left: 30px">共 {{ total }} 条</button>

  </div>
</template>

<script>

export default {
  name: "Pagination",
  props: ['pageNo', 'pageSize', 'total', 'continues'],
  computed: {
    totalPage() {
      // 向上取整
      return Math.ceil(this.total / this.pageSize)
    },
    startEndNum() {
      let { totalPage, pageNo, total, continues } = this //解构以后就不用写this了
      let start = 0,
          end = 0 //先定义两个变量存储起始数字与结束数字
      // 连续页码数字5【就是至少五面】，加果出现不正常的现象【就是不够五页】
      //不正常现象【总页数没有连续页码多】
      if (continues > total) {
        start = 1
        end = totalPage
      } else {
        // 正常现象【连续页码5，但是你的总页数一定是大于5的】
        start = pageNo - parseInt(continues / 2) //5/2就会出现不是整数
        end = pageNo + parseInt(continues / 2)
      }
      // 把出现不正常的现象【start数字出现0|负数】纠正
      if (start < 1) {
        start = 1
        end = continues
      }
      // 把出现不正常的现象【end数字大于总页数totalPage】纠正
      if (end > totalPage) {
        
        start = totalPage - continues + 1 
        end = totalPage
      }
      return { start, end }
    }
  },

}
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  height: 3.125rem;

  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: rgb(225,37,27);
      color: #fff;
    }

    &:hover {
      background-color: #d4d4d4;
    }
  }

}
</style>